<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>请求超时与网络异常</title>
    <style>
        #result{
            width:200px;
            height:100px;
            border:solid 1px #90b;
        }
    </style>
</head>
<body>
    <button id="btn1">点击发送请求</button>
    <div id="result"></div>
    <script>
        let btn1 = document.getElementById("btn1")
        let result = document.getElementById('result')
        btn1.onclick = function () {
            let xhr = new XMLHttpRequest()
            xhr.timeout = 2000
            xhr.ontimeout = function () {
                result.innerHTML = '请求超时'
            }
            xhr.onerror = function () {
                alert('你的网络似乎有一些问题')
            }
            xhr.open('GET','http://127.0.0.1:8000/delay')
            xhr.send()
            xhr.onreadystatechange = function () {
                if (xhr.readyState === 4){
                    result.innerHTML = xhr.response
                }
            }
        }

    </script>
</body>
</html>